<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #div1{
            width: 200px;
            height: 200px;
            background: skyblue;
            border-radius: 50%;
            position: absolute;
            right: 0;
            bottom: 0;
        }
    </style>
</head>
<body style="height: 2000px">
  <div id="div1"></div>

  <script>
      var timer = null;
      var oDiv = document.getElementById('div1');
      window.onscroll = function () {
          var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
          startMove(document.documentElement.clientHeight-oDiv.offsetHeight+scrollTop);
      };

      function startMove(iTarget) {
        clearInterval(timer);
        timer = setInterval(function () {
           var speed = (iTarget-oDiv.offsetTop)/10;
           speed = speed>0?Math.ceil(speed):Math.floor(speed);

           if(oDiv.offsetTop == iTarget){
               clearInterval(timer);
           }
           else{
               oDiv.style.top = oDiv.offsetTop+speed+'px';
           }

        },30)


      }



  </script>

</body>
</html>